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FAQ: CSH Coke Machine Information

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Archive-name: csh-coke-machine-info
Version: $Id: FAQ,v 1.2 1994/05/23 15:57:24 pat Exp pat $
Posting-Frequency: monthly

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    1. _A_Brief_Overview_of_The_Computer_Science_House_Coke_Machine_.
    2. _The_History_Of_Our_Machine_.
    3. _The_Hardware_In_The_Machine_.
    4. _The_Software_On_the_Unix_Side_.
    5. _The_Wide-Area_Access_Points_.
	a) graph
	b) xdrink
    6. _Current_Plans_for_the_Drink_Machine_.

1. _A_Brief_Overview_of_The_Computer_Science_House_Coke_Machine_.

    The following was only slightly modified from a mail message
    written by Tad Hunt (Wed, 27 Apr 1994 12:25:54 -0400)

	Our drink system is composed of several parts, the drink machine
    itself, the computer inside the machine, the serial connection to
    our drink server machine, the accounting software, and finally the
    wide area information systems (such as finger).

	The computer inside the drink machine is very simple.  It
    accepts commands to "drop" drinks from slots 1-5 (by sending
    an ascii '1'-'5' from the server), and a command to query status
    (an ascii 'A').  The computer drops drinks by tripping a relay to
    the solenoid on the particular slot requested.  The status returned
    is a bit pattern indicating if each slot is either full or empty
    (full is defined as one or more cans remaining) based on sensors
    in the slots.  All of this can be done through the wires that
    normally interface to the buttons on the front of the machine.

	On the server machine, there is a program called "drink" which
    keeps track of money in user accounts, how many cans are in each
    slot, the kind of drink in each slot, and how long the drink has
    been in the machine (for determining how cold it is).  This
    is the only program with permission to access "/dev/drink", which
    is the serial port the Coke Machine is connected to.  If the serial
    port isn't locked, it locks it, then querys the status of the
    machine to display a menu to the user, and allows them to choose
    a drink.  If the user has enough money in their account, and the
    slot isn't marked empty, the program asks for a time delay to wait
    before dropping the drink (in case the user needs to walk to the
    machine), then sends the command down the serial line to drop the
    appropriate drink.

	Finally comes the wide area information systems.  We setup an
    alias for one of our machines ( to answer
    requests for, and rewrote the finger program to
    display machine status by rsh(1)ing to the server machine and
    running the drink program in a mode to query machine statistics.
    Also added at this point was an XWindows drink client program,
    which uses command line options to "drink" to allow users to run
    an XWindows drink machine program and drop drinks by clicking a
    button.  You can run this program yourself -- if you have XWindows
    -- by doing the following:  "finger $",
    it will send "xdrink" to your display.  Also, you can get a graph
    of machine statistics by doing:  "finger"

	The drink system will soon be entering the "client-server" age
    with the addition of a debit daemon written by one of the drink
    support people, which will be useful for more than just drink, it's
    a generic debit system.  Most if not all of this  system will soon
    be available for anonymous ftp from in pub/drink.

2. _The_History_Of_Our_Machine_.

	Somebody here at RIT threw away a Coke Machine.  It was pretty
    beat up, but the members of Computer Science House plucked it from
    the trash none-the-less.  The Coke Machine was cleaned up and put
    to use.  It ran as a normal vending machine for some time in this

	But, as the red-tape flies, the company who owns the vending
    machine rights to the RIT campus complained that we were threatening
    their rights.  In a wonderous swirl of politics and crazy techies
    resulted in the Coke Machine being hooked up to the computer systems.
    For, as you see, a 'Vending Machine' is a machine that accepts
    money and gives out consumables in return.  We don't have a 'Vending
    Machine' so much as a high-tech group refrigerator.  The Coke Machine
    only accepts money or returns a drink.  If you're silly enough to put
    money in the little slot, you've lost your money.  If you've already
    given money to a drink admin, you can dispense a drink through the
    computer systems.

	Not long after that, a newer Coke Machine was donated to Computer
    Science House.  The first implementations of the Coke Machine were
    done on a small processor on a bread-board.  The newer implementation
    is a bit more 'rugged' (and explained below) in that many of the
    connections are actually soldered.  8^).

	This machine has been painted the CSH colors (purple and pink a la
    DEC/pdp).  It bears the Computer Science House name.  We're proud to
    have it on the Internet, but we must admit that CMU beat us to the
    punch.  Our big advantage over their machine though is the ability
    to drop a drink from where you sit and have it arrive at the same
    time you get to the machine.  Our machine has been the subject of
    little blurbs in major publications across the country and is listed
    as the 7th-most-fingered site by Wired magazine.  And, the current
    record for long-distance drops is Arizona to Rochester.

3. _The_Hardware_In_The_Machine_.

	The computer in the machine is a small 8051 board with a serial
    connection, LCD display, A/D convertor, and several out ports.  The
    EPROM that this board runs from contains code written by Sean
    McGranaghan.  That code is loosely based on code written by Frank
    Giuffrida for that board's intended purpose as power-supply monitor
    and regulator.

	As is mentioned above, this software simply reads the status
    lines that were at one time hooked up to the LED indicators on the
    buttons of the machine to check the fullness of a slot.  In its
    current incarnation, the sensor on the Jolt slot tends to stick
    in the 'Empty' position.  Fortunately for us caffeine mongers, the
    'Empty' indicator can be ignored.

	If a request for status is received on the serial line, a bit
    mask is formed indicating which slots are full.  This bit mask is
    sent back over the serial line to the waiting program that made
    the request.  In this mask, the bits 0 through 4 are used to
    represent the 5 slots on the machine.  The 5th bit is also set to
    ensure that the return value is a printable ascii character and as
    a verification that it actually did check the slots.

	If an ascii digit on the range '1' - '5' is sent to this board,
    it triggers a solid-state relay which closes the circuit that would
    normally be closed by pressing the button on the front of the machine.
    If this is successful, a 'D' is transmitted back to the waiting
    program.  If this fails, an 'E' is sent back to the waiting program.
    ('D' is for drop.  'E' is for error.)

	The LCD on the board constantly displays a message
    'CSH Coke Machine' and the amount of time since the board
    has been reset in the form 'Day 000 00:00:00'.

	Currently, several schemes are being considered for this board to
    verify that it is talking to some program and not to someone with
    tip(1) access to the device.  This will make the Coke Machine no more
    vulnerable to root attack than user attack.

4. _The_Software_On_the_Unix_Side_.
	The board in the Coke Machine is connected to a CCI Power 6/32
    Tahoe that is currently running BSD 4.3 Shanzer (a custom blend
    of 4.3 Reno, 4.3 Tahoe, and 4.4 Alpha).  /dev/drink is configured
    as a 9600-baud connection to the board in the Coke Machine.  The
    connection is over a standard RS232 connection.

	The software consists, currently, of one main program called
    'drink'.  drink(1) maintains a database of user balances and
    statistics as well as slot statistics.  This software has undergone
    many revisions (read: total rewrites) over the years.  I'm pretty
    sure that I'm the only one who will admit to having touched it.
    But, I'll drag in Bob Krzaczek's name into it to as the last person
    to touch the stuff I hacked on.

	In its current incarnation, this software keeps track of
    user balances in CSH-franks.  These bear a striking relation
    to US-dollars in that the exchange rate has always been 100
    CSH-franks to 1 U.S. Dollar.  But, such relationships are
    human constructions and probably just coincidences that reflect
    deep underlying symmetries in the web of the Universe (or not)
    [much like the way RIT student ids resemble, but are distinct from,
    social security numbers].  CSH-franks are known by some as
    CSHmids and CSH-wonder-wubbas.  But... the last 6 minutes of
    voting turned up 2 votes for CSH-franks, 1.5 votes for CSH-bobas,
    several incoherent mumbles about Pink Floyd, a compromise for
    and not much else in the close-to-relevant category.  [If Ross
    Perot was ever part of a CSH wall(1) war, he'd think twice about
    electronic town-meetings.]

	The drink(1) program offers several command line options.  These
	-o [12345rg]	where a number specifies a slot to drop a drink
			from, 'r' specifies to drop a drink from a random
			slot (choosing from the full-ones), and 'g' is
			a special gamble option (to be described later).

	-d N		delays for N seconds before dropping the drink.

	-l login	useful for dropping a drink from the balance
			of the user given by 'login'.  This option
			prompts you for a password to validate you.

	-m		forces menu mode where the current slot statistics
			are displayed.
	-b		shows the user's balance.

	-s		shows the user's raw statistics as number of
			drinks dropped per slot.

	-S		shows the user's statistics in relation to the
			global statistics.  This options shows number
			of drinks dropped by the user on a per-slot basis
			and the number of drinks dropped overall on
			a per-slot basis and the percentage per-slot
			the user makes up.  For example, for me, now,
			I have dropped 382 of 2412 drinks dropped from
			slot 5 since last time the statistics were
			cleared.  I account for 15.8375 percent of the
			drops from slot 5 (Coke Classic).  Also given
			in these statistics is the current gamble cost
			and the accumulated gamble (to be explained later).

	-t		shows the number of drinks in each slot divided
			into time slots.  Along the vertical, each slot
			is shown.  Across the horizontal, the number
			of drinks in the slot for less than one hour,
			between one and three hours, more than
			three hours, and the total in the slot is shown.

	-T		This option is similar to the last but it puts
			out the information in a form easily readable by
			other programs.  First, it puts out the current
			time as returned by time(2).  Then, it puts out
			on the following the title of the first slot and
			a string representing how many drinks are in the
			slot and what times they were placed there.  This
			string is of the form:
			    number time number time number time 0
			All time(2) values are printed in hexidecimal.
			These couplets are repeated for each slot.

	The gamble option was originally designed to make use of the
    fact that the drink machine isn't always full and the fact that people
    may not have enough of a balance to afford a drink.  With the gamble
    option, the cost of gambling is computed by adding up the prices of
    all of the full slots, dividing by the total number of slots and adding
    the 'gamble cost'.  The 'gamble cost' is currently 2 CSH-franks.
    This is a fudge-factor to favor drink staying in the black.  The more
    slots that are empty, the lower the cost.  The current risk is 12
    CSH-franks, but the odds of getting a drink are only 1 in 5
    (and that slot is the Diet Mystery Slot (a double whammee)).  A side
    goal is to integrate a 'Coke' as a potion in some deep dungeon in
    nethack and, if you quaff it, and the accumulated gamble cost is
    greater than than the price of a Coke, it'll drop you one.  The current
    accumulated gamble cost is 262 CSH-franks.

5. _The_Wide-Area_Software_.

	If you have finger(1) access, X access, or Mosaic(1) access, you
    can witness our Coke Machine first-hand from where you sit.  There
    are two main pathways to our Coke Machine through the Internet.  These
    are through Tad Hunt's modified finger(1) and
    through Eric Van Hensbergen's xdrink(1) interface.  Both of these
    can be accessed from the CSH Drink Machine page on the World Wide
    Web.  The URL for that page is:
5a) graph
	One of the first bits of net access we allowed to our Coke
    Machine was to finger(1) it to get information.  The current state
    of the Coke Machine can be divined in several ways through finger(1).
    Tad Hunt rewrote the finger(1) program at to
    handle several virtual users.  The first of these can be accessed
    by fingering  This will display an
    informational message and an ascii representation of the Coke Machine.
    This representation includes the price at each slot, the number of
    drinks in each slot, and a graph representing the coldness of those
    drinks.  Emprical tests have shown that complete coldness of a drink
    is achieved in three hours.

	A different view of the contents of the coke machine can be
    obtained by fingering  There is a great
    deal of redundant information in this, but.... what can you do?

	Fingering will provide more information
    into the ways to finger the coke machine.

	And, if you're running X-windows, a command like
    'finger` or
    'finger ${DISPLAY}' should bring up an X-interface
    to our drink software on your display.

b) xdrink

	The xdrink(1) interface was written by Eric Van Hensbergen.
    It presents bitmaps for each of the slots (they easily get out
    of date (sorry)).  It offers a pointy-clicky interface for those
    not too keen on command lines.  It represents the fullness of
    each slot with a bar-graph, the contents with a bitmap, and the
    mystery-slot as a flashing pattern of the bitmaps.

6. _Current_Plans_for_the_Drink_Machine_.

	I am currently almost finished with a new incarnation of the
    drink software.  This incarnation involves a 'telnet' interface
    similar to those of 'smtp' and 'ftp'.  It also provides a means
    for kerberos authentication.  Additionally, it will talk several
    languages from English to German to Esperanto to Lojban to Rot13
    (English) to Piglatin (English).  More on this as it's available.
    Also, in this incarnation, one will be able to risk any amount of
    money above the gamble cost, choosing their desired slot, and having
    odds proportional to the amount risked divided by the cost of the
    desired drink.

For more further questions or to arrange a personal tour of Computer Science
House, mail
 "Hot Hands of an Oslo Dentist"

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